My question is whether there are certain limitations to accessing COM objects when you're dealing with an MSIX-packaged app.
I've created a blank WinUI 3 C++ project, using the Visual Studio project template. In the project, I've created a traditional COM class that's registered at runtime using CoRegisterClassObject. I do not otherwise register the object in the registry. It's a singleton that's supposed to be accessible only when the .exe is already launched.
Now when I modify the project to be unpackaged, and the .exe is launched, I'm able to access the singeton class from another process, by calling CoCreateInstance. Everything works as designed.
But when I change the MSIX project back to the packaged setup, the call to CoCreateInstance from the unpackaged process now fails, with code REGDB_E_CLASSNOTREG.
It's like trying to connect to a COM object when there's an unelevated/elevated mismatch. Same error.
So are unpackaged processes unable to access COM objects registered with CoRegisterClassObject in MSIX-packaged apps? Is there a workaround or anything? Thanks in advance.
I am working on a project for a Windows library in Ada that must be compiled in a DLL, starting from a .gpr project via GPRBuild. I was able to produce a working DLL for Windows, but now I want to specify the base address for the location of the DLL. At the moment I was able to set the DLL location through the editbin utility but I would like to integrate this step directly in the .gpr file. I have tried to use the Library_Options attribute:
for Library_Options use ("-Wl,--disable-auto-image-base", "-Wl,--image-base=0x20000000");
But it does not seem to help. Is it somehow possible to do what I want directly after compilation or is it really necessary to use an external script?
I have a unmanaged C++/ATL in-process COM object (in Unmanaged.dll) that I'm trying to use from a managed C# DLL (Managed.dll). However, I want I want to use registration free COM. I have it down to these steps:
Register the COM object on the development machine. The in-process server must have a properly registered type library.
Add a reference to the COM object within the C# project, and then set the Reference Properties to Isolated = True.
This produces Unmanaged.dll, Managed.dll, and Native.Managed.manifest. Opening the manifest, it's pretty clear how the system uses it to load the COM object in a registration-free way.
Here's the rub. I have a managed EXE (Managed.exe) which dynamically loads Managed.dll to access public types. What I mean by "dynamically" is, it uses Assembly.LoadFrom("Managed.dll"). When the code inside Managed.dll tries to create the COM object, it gets a "class not registered" exception. It appears the activation context doesn't get setup correctly when Managed.dll gets loaded.
Is there a way to get registration free COM to work in this scenario?
Two days without an answer, so here's what I've come up with in that time...
It does indeed look like the activation context is setup by the OS at process launch based on the manifest associated with the main EXE. That means all registration-free COM related elements must be in the Main.exe.manifest at the time the process is started. This breaks the isolation between EXE and DLLs. If a DLL is responsible for creating COM objects, you wouldn't expect the EXE manifest to have to contain the reg-free COM information. You might have expected the manifest associated with the DLL to be merged into the process activation context at the time the DLL gets loaded, but it does not.
To work around this, the DLL must configure a new activation context before creating the COM object. To make things worse, there is currently (as of .NET 4.0) no managed way to do this. So, the DLL will have to PInvoke the following Win32 functions:
CreateActCtx
ActivateActCtx
DeactivateActCtx
ReleaseActCtx
I wrapped these calls with a managed class that calls CreateActCtx and ActivationActCtx in the constructor and DeativateActCtx and ReleaseActCtx in IDisposable::Dispose.
The native PRISM's modulariy mechanism support loading modules by path to assembly, containiтg this module. I want to have availability to store modules' views (XAML) in database in order end user could change and customize them. Database is chosen as it is simpler to store and retrieve information and requires no recompilation and making of binaries.
The problem is that View consists of XAML and codebehind and we need to divide(?) them and store separately and when we need them we must clue them and load to module (with reflection or something else?) but I don't know how and if it is possible at all?
I see two options here. The easy way or the hard way.
The easy way is to have all the assemblies on the drive, and have a PRISM module catalog that loads them depending on settings from a database.
The hard way is to put the assemblies into the database, and have the module catalog load the assemblies from there. You'd have to encode the assembly, probably using Base64, put it into the database, and then reload the assembly from the database.
To reload an assembly from a database record, you can use the same mechanism as the DirectoryModuleCatalog. Copy that class and change it so it loads the assemblies from the stream coming from the DB instead of a file from a directory.
How exactly do DLL files work? There seems to be an awful lot of them, but I don't know what they are or how they work.
So, what's the deal with them?
What is a DLL?
Dynamic Link Libraries (DLL)s are like EXEs but they are not directly executable. They are similar to .so files in Linux/Unix. That is to say, DLLs are MS's implementation of shared libraries.
DLLs are so much like an EXE that the file format itself is the same. Both EXE and DLLs are based on the Portable Executable (PE) file format. DLLs can also contain COM components and .NET libraries.
What does a DLL contain?
A DLL contains functions, classes, variables, UIs and resources (such as icons, images, files, ...) that an EXE, or other DLL uses.
Types of libraries:
On virtually all operating systems, there are 2 types of libraries. Static libraries and dynamic libraries. In windows the file extensions are as follows: Static libraries (.lib) and dynamic libraries (.dll). The main difference is that static libraries are linked to the executable at compile time; whereas dynamic linked libraries are not linked until run-time.
More on static and dynamic libraries:
You don't normally see static libraries though on your computer, because a static library is embedded directly inside of a module (EXE or DLL). A dynamic library is a stand-alone file.
A DLL can be changed at any time and is only loaded at runtime when an EXE explicitly loads the DLL. A static library cannot be changed once it is compiled within the EXE.
A DLL can be updated individually without updating the EXE itself.
Loading a DLL:
A program loads a DLL at startup, via the Win32 API LoadLibrary, or when it is a dependency of another DLL. A program uses the GetProcAddress to load a function or LoadResource to load a resource.
Further reading:
Please check MSDN or Wikipedia for further reading. Also the sources of this answer.
What is a DLL?
DLL files are binary files that can contain executable code and resources like images, etc. Unlike applications, these cannot be directly executed, but an application will load them as and when they are required (or all at once during startup).
Are they important?
Most applications will load the DLL files they require at startup. If any of these are not found the system will not be able to start the process at all.
DLL files might require other DLL files
In the same way that an application requires a DLL file, a DLL file might be dependent on other DLL files itself. If one of these DLL files in the chain of dependency is not found, the application will not load. This is debugged easily using any dependency walker tools, like Dependency Walker.
There are so many of them in the system folders
Most of the system functionality is exposed to a user program in the form of DLL files as they are a standard form of sharing code / resources. Each functionality is kept separately in different DLL files so that only the required DLL files will be loaded and thus reduce the memory constraints on the system.
Installed applications also use DLL files
DLL files also becomes a form of separating functionalities physically as explained above. Good applications also try to not load the DLL files until they are absolutely required, which reduces the memory requirements. This too causes applications to ship with a lot of DLL files.
DLL Hell
However, at times system upgrades often breaks other programs when there is a version mismatch between the shared DLL files and the program that requires them. System checkpoints and DLL cache, etc. have been the initiatives from M$ to solve this problem. The .NET platform might not face this issue at all.
How do we know what's inside a DLL file?
You have to use an external tool like DUMPBIN or Dependency Walker which will not only show what publicly visible functions (known as exports) are contained inside the DLL files and also what other DLL files it requires and which exports from those DLL files this DLL file is dependent upon.
How do we create / use them?
Refer the programming documentation from your vendor. For C++, refer to LoadLibrary in MSDN.
Let’s say you are making an executable that uses some functions found in a library.
If the library you are using is static, the linker will copy the object code for these functions directly from the library and insert them into the executable.
Now if this executable is run it has every thing it needs, so the executable loader just loads it into memory and runs it.
If the library is dynamic the linker will not insert object code but rather it will insert a stub which basically says this function is located in this DLL at this location.
Now if this executable is run, bits of the executable are missing (i.e the stubs) so the loader goes through the executable fixing up the missing stubs. Only after all the stubs have been resolved will the executable be allowed to run.
To see this in action delete or rename the DLL and watch how the loader will report a missing DLL error when you try to run the executable.
Hence the name Dynamic Link Library, parts of the linking process is being done dynamically at run time by the executable loader.
One a final note, if you don't link to the DLL then no stubs will be inserted by the linker, but Windows still provides the GetProcAddress API that allows you to load an execute the DLL function entry point long after the executable has started.
DLLs (dynamic link libraries) and SLs (shared libraries, equivalent under UNIX) are just libraries of executable code which can be dynamically linked into an executable at load time.
Static libraries are inserted into an executable at compile time and are fixed from that point. They increase the size of the executable and cannot be shared.
Dynamic libraries have the following advantages:
1/ They are loaded at run time rather than compile time so they can be updated independently of the executable (all those fancy windows and dialog boxes you see in Windows come from DLLs so the look-and-feel of your application can change without you having to rewrite it).
2/ Because they're independent, the code can be shared across multiple executables - this saves memory since, if you're running 100 apps with a single DLL, there may only be one copy of the DLL in memory.
Their main disadvantage is advantage #1 - having DLLs change independent your application may cause your application to stop working or start behaving in a bizarre manner. DLL versioning tend not to be managed very well under Windows and this leads to the quaintly-named "DLL Hell".
DLL files contain an Export Table which is a list of symbols which can be looked up by the calling program. The symbols are typically functions with the C calling convention (__stcall). The export table also contains the address of the function.
With this information, the calling program can then call the functions within the DLL even though it did not have access to the DLL at compile time.
Introducing Dynamic Link Libraries has some more information.
http://support.microsoft.com/kb/815065
A DLL is a library that contains code
and data that can be used by more than
one program at the same time. For
example, in Windows operating systems,
the Comdlg32 DLL performs common
dialog box related functions.
Therefore, each program can use the
functionality that is contained in
this DLL to implement an Open dialog
box. This helps promote code reuse and
efficient memory usage.
By using a DLL, a program can be
modularized into separate components.
For example, an accounting program may
be sold by module. Each module can be
loaded into the main program at run
time if that module is installed.
Because the modules are separate, the
load time of the program is faster,
and a module is only loaded when that
functionality is requested.
Additionally, updates are easier to
apply to each module without affecting
other parts of the program. For
example, you may have a payroll
program, and the tax rates change each
year. When these changes are isolated
to a DLL, you can apply an update
without needing to build or install
the whole program again.
http://en.wikipedia.org/wiki/Dynamic-link_library
DLL is a File Extension & Known As “dynamic link library” file format used for holding multiple codes and procedures for Windows programs. Software & Games runs on the bases of DLL Files; DLL files was created so that multiple applications could use their information at the same time.
IF you want to get more information about DLL Files or facing any error read the following post.
https://www.bouncegeek.com/fix-dll-errors-windows-586985/
DLLs (Dynamic Link Libraries) contain resources used by one or more applications or services. They can contain classes, icons, strings, objects, interfaces, and pretty much anything a developer would need to store except a UI.
According to Microsoft
(DLL) Dynamic link libraries are files that contain data, code, or resources needed for the running of applications. These are files that are created by the windows ecosystem and can be shared between two or more applications.
When a program or software runs on Windows, much of how the application works depends on the DLL files of the program. For instance, if a particular application had several modules, then how each module interacts with each other is determined by the Windows DLL files.
If you want detailed explanation, check these useful resources
What are dll files , About Dll files